Using Expressions
A JSP
expression
element
is used to insert the result of a scripting code expression into the
response. It’s the Java scripting equivalent to an
EL expression directly in template text. An expression starts with
<%=
and ends with %>
.
Note that the only syntax difference compared to a scriptlet is the
equal sign (=
) in the start identifier. Examples
are:
<%= userInfo.getUserName( ) %> <%= 1 + 1 %> <%= new java.util.Date( ) %>
The result of the expression is written to the response body,
converted to a String
if needed. One thing is
important to note: as opposed to statements in a scriptlet, the code
in an expression must not end with a semicolon. This is because the
JSP container combines the expression code with code for writing the
result to the response body. If the expression ends with a semicolon,
the combined code will not be syntactically correct.
As with EL expressions, a Java expression can also be used to assign a dynamic value to an action element attribute, but with a few restrictions as described later in this chapter.
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